5) 



NEW NORTH AMERICAN EARTHWORMS 161 



Important characters of the genus Megascolides as given by 

 Stephenson (1930, p. 835) are: "Setae eight per segment. Sper- 

 mathecal pores one to five pairs, the last in furrow Y/8 or 8/9 or on 

 segment ix. One gizzard in the region of segments v and vi. 

 Micronephridial at least in the anterior part of the body, often 

 throughout. Prostates tubular, with simple unbranched canal " 

 Equally important are certain other characters found also in some 

 other genera of the subfamily Megascolecinae. Each of the ducts 

 of the one pair of prostate glands is united with the sperm duct 

 or ducts of the same side of the worm, and they open in common on 

 somite 18. 



MEGASCOLroES AMERICANUS Smith 



Megascolides americanus Smith, Amer. Nat., vol. 31, p. 203, 1897. 



Distinguishing characters. — Length of fairly well extended speci- 

 mens, 180-190 mm. Diameter, 6-7 mm. Number of somites in 

 eight specimens averaged 235. Setal distances in anterior part, 

 approximately aa : ah : he : cd'= 10 : 2 : 8 : 4 ; and posterior to the 

 clitellum aa'.ah:hG\ cd=12 : 3 : 7 : 4; dd in the anterior part is about 

 two-thirds of the circumference and posteriorly is but little more 

 than one-half of the circumference. Penial setae on 18, very closely 

 paired, long, slender, curved in sagittal plane, with distal one-third 

 projecting posteriad from openings, and finely sculptured near tips. 

 The clitellum includes 13-22 and part of 23; incomplete ventrally; 

 reddish tan color. Circular, median, ventral papillae on 14/15, 

 15/16, and 16/17; paired ventral papillae on 19/20, 20/21, and in 

 some specimens on 21/22. A pair of prominent transversely elongate 

 papillae on 18, bearing penial setae and male pores. Spermathecal 

 pores on 7/8 and 8/9. 



Septa 7/8-11/12 are strongly thickened, 6/7 and 12/13 less thick- 

 ened. Calciferous gland in 11-15 and less definitely developed than in 

 some species. The two sperm ducts of either side unite in 16, and 

 the common duct thus formed opens into the proximal part of the 

 prostate duct of the same side. Spermathecae paired in 8 and 9. 



Exterrml characters. — Presumably owing to differences in treat- 

 ment when they were preserved, the four specimens collected in 

 1896 at Pullman, Wash., were less contracted than were the five 

 specimens collected there in 1931. In some specimens in each col- 

 lection the diameter in the region of 18 is not much more than one- 

 half as great as that near 8 and 30, where the diameter is at a maxi- 

 mum. The average length of specimens in the earlier collection is 

 180-190 mm and the maximum diameters 6-7 mm ; while the length 

 of those in the later collection is 150-160 mm and the maximum di- 

 ameters 8-10 mm. One specimen in the earlier collection was ap- 



